Various light sources have been proposed for therapy of different dermatological problems. For example, blue light in the range of 400-420 nm or 400-450 nm or has been found helpful for acne treatment. U.S. Pat. No. 6,835,202 describes a device for acne treatment having spectrum 405-440 nm. Red light at 590 nm and 632 nm is used for skin rejuvenation and U.S. Pat. No. 6,676,655 describes a method of skin treatment using devices emitting light in narrowband multichromatic spectrum having the wavelengths corresponding to tissue absorption peaks. U.S. Pat. No. 6,645,230 describes devices for photodynamic therapy using specific light spectrum ranges.
Although some wavelengths of the electromagnetic spectrum have strong therapeutic effect, the full broad spectrum of sunlight, (which includes ultraviolet, visible and infrared ranges) is known to have deleterious effects on the skin. For example, exposure to direct sunlight is a major reason for skin damage and premature aging, and (particularly the ultraviolet component) can cause skin cancer.